This invention relates to pressurized vessels such as kegs for storing, transporting and dispensing beverages. The invention relates particularly to a closure for a keg, the closure having a safety mechanism to prevent the closure being re-closed after use. This ensures that the keg cannot be left pressurized after use and also that it cannot be refilled with the closure being re-closed afterwards.
Kegs are widely used for the distribution and service of beverages such as beer. A closure in a neck of the keg typically includes a filling and dispensing valve that defines multiple flow paths through the closure. In this way, during filling when the keg is usually inverted, beverage can be injected into the keg through the closure via a first flow path while displaced gas can exit the keg through the closure via a second flow path. Conversely, during dispensing, a propellant gas (typically nitrogen or carbon dioxide) can be injected into the keg through the closure via the first flow path to force beverage out of the keg through the closure along the second flow path. In the most common ‘well-type’ and ‘flat type’ arrangements, the closure comprises one or more valve elements and concentric flow paths.
When filling the keg at a filling station on a production line, the keg is usually inverted for use with beer and carbonated soft drinks although it could be upright for other beverages, especially those without effervescence, and a filling head is coupled to the closure to form a seal with the closure. The filling head has one or more formations that press against one or more spring-loaded valve elements of the closure to open the flow paths through the closure. Air inside the keg is flushed out with a relatively inert gas, for example carbon dioxide, and beverage is then injected into the keg via a liquid line connected to the filling head. Gas displaced from the keg by the incoming beverage is forced out through a vent in the filling head. When the keg is removed from the filling station, the filling head is uncoupled from the closure and the one or more valve elements of the closure therefore snap shut under spring loading, sealing the beverage and any remaining inert gas within the keg.
For the purpose of dispensing the beverage, a dispense head is coupled to the closure to form a seal with the closure. The dispense head has a lever that, when depressed, extends one or more plungers corresponding to the formations of the filling head. The plunger(s) therefore press against one or more valve elements of the closure to re-open the flow paths through the closure. Those flow paths communicate with gas and liquid lines connected to the dispense head. A propellant gas is injected into the keg from an external source connected to the gas line. Beverage is then forced out of the keg when a tap in the liquid line is opened to dispense the beverage.
When the dispense head is coupled to the closure, the propellant gas is injected into the keg at super-atmospheric pressure. The keg will remain under super-atmospheric pressure unless and until that gas is vented. It is recommended for safety purposes to vent the propellant gas from the keg when the dispense head is uncoupled from the closure, most commonly when the keg has been emptied and is being interchanged with a fresh, full keg. For this purpose, some dispense heads have a purge valve that is operable to vent propellant gas from the keg before the dispense head is uncoupled from the closure.
However, not all dispense heads have a purge valve and even those that do have a purge valve may not be operated correctly. In practice, a user will often be in a hurry to swap empty kegs for full kegs while dispensing beverages in a busy bar and may not therefore take the time necessary to vent the propellant gas from the empty keg. Instead, the user may simply remove the dispense head from the closure, allowing the spring-loaded valve element(s) of the closure to snap shut and hence to close the flow paths through the closure. The result is that the empty keg remains pressurized, which may not be apparent upon viewing the keg. This is a particular problem where a keg is of flexible material such as blow-moulded polyethylene terephthalate (PET), which is intended to allow the keg to be crushed after use for recycling rather than being returned intact for refilling like a rigid metal keg. Clearly a pressurized keg is not easily crushable. Also, in safety terms, it is undesirable for a pressurized keg to be punctured or ruptured, for example if an attempt is made to crush the keg during waste disposal while believing that the keg is not pressurized.
Another problem is that if the valve element(s) of the closure can still be opened and closed after the original beverage has been dispensed, the keg could possibly be re-filled in an unauthorised manner. For example, the keg could be re-filled with a beverage that is not of the appropriate quality; certainly, the keg is unlikely to be re-filled under the controlled conditions necessary to deliver a beverage in optimum condition. This is particularly undesirable as the keg may bear the brand of the original beverage supplier, whose reputation may be damaged by apparently supplying an inferior product. The keg could even be re-filled with a liquid that is not intended for human consumption and that could be dangerous to drink. Unauthorised refilling may not be apparent from a cursory inspection of the keg.
For these reasons, various keg closures have been proposed in which a valve element can close after filling but cannot close again after dispensing. For example, the proposal disclosed in U.S. Pat. No. 4,909,289 to Hagan et al employs a ratchet arrangement that limits the number of valve openings to allow keg testing and keg filling procedures before the valve element locks open after dispensing.
The proposal in U.S. Pat. No. 4,909,289 is impractical for various reasons. For example, the number of parts in its mechanism, and the way in which those parts interact, leads to long tolerance chains. This renders the mechanism vulnerable to failure where the combined tolerance of the parts causes excessive dimensional fluctuations between different assemblies. Also, the mechanism is not capable of handling the wide variety of filling heads and dispense heads that are available on the market.
A later proposal disclosed in DE 10 2007 036 469 to Schäfer Werke involves depressing a valve element to a lesser extent upon coupling a filling head to the closure for filling (i.e. the filling stroke) and to a greater extent upon coupling a dispense head to the closure for dispensing (i.e. the dispense stroke). The greater movement of the valve element through the dispense stroke causes the valve element to lock in a depressed position such that when the dispense head is removed after dispensing, the valve element cannot move back to the closed position.
The proposal disclosed in DE 10 2007 036 469 requires the filling stroke to be shorter than the dispense stroke. However, the use of a well-type or flat-type fitting involves a filling stroke that is often equal to or sometimes longer than the dispense stroke. The proposal in DE 10 2007 036 469 cannot handle situations where the filling stroke is longer than or equal to the dispense stroke because the valve element will either lock open prematurely during the filling procedure or will fail to lock open after the dispensing procedure.
It is against this background that the present invention has been devised.
The invention resides in a closure for a pressure vessel such as a keg, the closure comprising: at least one valve element that is movable with respect to the housing, inwardly into an open state and outwardly into a closed state; and a lock mechanism having a locking element that is movable with respect to the housing and is capable of holding the valve element in the open state; wherein the lock mechanism includes first and second couplings at which the locking element and the valve element are mutually engageable, and is arranged such that when the locking element and the valve element are engaged at the first coupling, the locking element moves with the valve element as the valve element moves from the open state into the closed state, said movement of the locking element enabling engagement between the locking element and the valve element at the second coupling, which engagement at the second coupling occurs on subsequent movement of the valve element into the open state to prevent the valve element returning to the closed state.
The lock mechanism employed by the invention does not suffer from the long tolerance chains of U.S. Pat. No. 4,909,289 or the inability of U.S. Pat. No. 4,909,289 to handle the variety of filling heads and dispense heads that are on the market. Also, unlike DE 10 2007 036 469, the mechanism of the invention can be used even if the filling stroke is equal to or longer than the dispense stroke.
In the preferred embodiment of the invention to be described below, the first coupling is disposed outwardly with respect to the second coupling.
Preferably, the couplings are defined by ratchet formations acting between the locking element and the valve element for substantially unidirectional outward movement of the locking element with respect to the housing. Advantageously, the ratchet formations provide reliable movement between the locking element and the valve element.
Preferably, the valve element is movable with respect to the housing along an axis, the locking element is movable axially with respect to the housing in response to said axial movement of the valve element, and the couplings comprise axially-spaced engaging formations acting between the locking element and the valve element. Advantageously, axial movement simplifies and so improves the reliability of the closure.
Preferably, following engagement between the locking element and the valve element at the first coupling, outward movement of the valve element moves the locking element to a position within the housing in which further outward movement of the locking element with respect to the housing is limited in extent.
Preferably, following engagement between the locking element and the valve element at the second coupling, further outward movement of the locking element is limited by encountering a stop formation fixed relative to the housing.
Preferably, following engagement between the locking element and the valve element at the first coupling, outward movement of the valve element moves the locking element to a position within the housing in which inward movement of the locking element with respect to the housing is limited in extent.
Preferably, upon moving outwardly with the valve element, the locking element passes a ratchet formation that restrains inward movement of the locking element. The ratchet formation may be a shoulder fixed relative to the housing.
Preferably, the locking element comprises an opposed formation arranged to engage with the ratchet formation.
Preferably, following movement of the valve element from the open state into the closed state, the locking element lies between opposed limit formations disposed respectively outward of an outer end and inward of an inner end of the locking element.
Preferably, the limit formations comprise the stop formation and the ratchet formation.
Preferably, the couplings comprise resilient snap-fit formations engageable by relative sliding movement of the valve element with respect to the locking element.
Preferably, the couplings comprise first and second coupling components on the locking element that are engageable successively by a coupling component on the valve element upon successive opening strokes of the valve element.
Of course, the inventive concept extends to a pressure vessel such as a keg, supplied with or fitted with the closure of the invention.
The first and second embodiments of the present invention relate to a keg closure functionally and in key dimensions with existing keg closures known in the art as ‘Flat Type’, ‘Type A’ or ‘Flat Type A’ keg closures. As such, dispensing or filling heads suitable for use with such ‘Flat Type A’ keg closures can also be used in conjunction with the closure of the first and second embodiments of the present invention.